root vegetable       
noun [ C ] uk/ˌruːt ˈvedʒ.tə.bəl/ us/ˌruːt ˈvedʒ.tə.bəl/
 根菜类,根茎类蔬菜
a vegetable such as a carrot or turnip that is the root of a plant
  Root vegetables, such as carrots, parsnips, and beetroot, are great for slow cooking. 根茎类蔬菜,如胡萝卜、欧芹、甜菜根等,非常适合慢炖。 
 It's superb served with oven-roasted root vegetables. 搭配烤箱烤制的根茎类蔬菜,是极好的选择。 
 - More examples
 - Scrub root vegetables with a clean vegetable brush.
 - Salsify is a root vegetable with a delicate flavour.
 - This is a main dish soup made with lamb and root vegetables and leeks.